Millermatic 200

The big difference between a harbor freight welder and a miller? Is that a joke? The harbor freight welder sucks, the miller doesn't!

I'd buy a Millermatic 200 in a heartbeat. I run a millermatic 35, which is an earlier version that's rated at 150 amps and runs off of 220v. My 35 is a little bit of a step down from the later 200, but its probably closer to the later 200 than a 100. A millermatic 200 will be fine for sheet metal, and has the added bonus of being useful for a lot of heavier welding.

The biggest thing to pay attention to with welders is the duty cycle. That's what separates cheap welders from good ones. A Millermatic 200 has a 60% duty cycle at 200 amps, meaning, you can weld at 200 amps for 6 out of every 10 minutes. It also means that at 150 amps, it has a 100% duty cycle, ie, you can weld all day without stopping. A harbor freight 180 has a 20% duty cycle at 140 amps. Meaning, you can only weld for 2 out of every 10 minutes without overheating the machine. This is because cheap welders use aluminum for all their internal windings, and it will straight up melt if you exceed your duty cycle. Better welders use copper for all their windings, and they have better duty cycles and more durability. The cheap crap (like the HF 180) also use flux core wire instead of gas shielding. Flux core sucks for sheetmetal, as it spatters all over the place. Lots more work grinding it all off later.

Most sheetmetal will need less than 100 amps to weld it. A millermatic 200 is definitely overkill for sheet metal, but it will weld it without issue. A 100 would be fine, and cheaper and lighter, and run off 110v and all that good stuff. But, it will be topped out welding sheet metal too, so, that's pretty much where its usefulness will end.

If all you're looking to do is "hot glue gun" some sheet metal together and never use the welder again, you'll probably be fine with anything. But if you actually want a capable welder, something that you can use later on any number of jobs, a millermatic 200 would be a great buy.

I see Millermatic 200's listed on eBay for around $1k, which is half of what a new millermatic retails for. Locally you might be able to find them under $1k, which would be a steal for a capable machine like that. If I remember correctly, I paid around $400 for my 35, but that's a '70's era machine. The nice thing about Miller is that they still support their older welders, so you can still get parts, manuals etc, even for stuff that's 40+ years old.